Rotatable transverse flux electrical machine

ABSTRACT

The invention concerns a rotatable transverse flux electrical machine (TFEM) comprising a stator portion; and a rotor portion rotatably located in respect with the stator portion, the rotor portion including an alternate sequence of magnets and concentrators radially disposed about a rotation axis thereof; the stator portion including at least one phase, the at least one phase including a plurality of cores cooperating with a coil disposed about the rotation axis, each core including a skewed pair of poles to progressively electromagnetically engage an electromagnetic field of respective cooperating concentrators. The invention is also concerned with a plurality of elements located in desired positions in the TFEM and also with a linear TFEM.

CROSS REFERENCE

The present application relies to, is a non-provisional application of,and claims priority under 35 U.S.C. 119(e) to U.S. provisionalapplication No. 61/679,476, filed Aug. 3, 2012, entitled TRANSVERSE FLUXELECTRICAL MACHINE, which is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to rotatable transverse flux electricalmachines. The present invention more specifically relates to transverseflux alternators and motors producing low cogging torque and rippletorque.

2. Description of the Related Art

Alternators and motors are used in a variety of machines and apparatusesto produce electricity from mechanical movements. They find applicationsfor energy production and transportation, to name a few. Alternators andmotors can use Transverse Flux Permanent Magnet (TFPM) technologies.

Transverse flux machines with permanent magnet excitation are known fromthe literature, such as the dissertation by Michael Bork, Entwicklungand Optimierung einer fertigungsgerechten Transversalfluβmaschine[Developing and Optimizing a Transverse Flux Machine to Meet ProductionRequirements], Dissertation 82, RWTH Aachen, Shaker Verlag Aachen,Germany, 1997, pages 8 ff. The circularly wound stator winding issurrounded by U-shaped soft iron cores (yokes), which are disposed inthe direction of rotation at the spacing of twice the pole pitch. Theopen ends of these U-shaped cores are aimed at an air gap between thestator and rotor and form the poles of the stator. Facing them,permanent magnets and concentrators are disposed in such a way that themagnets and concentrators that face the poles of a stator core have theopposite polarity. To short-circuit the permanent magnets, which in therotor rotation are intermittently located between the poles of thestator and have no ferromagnetic short circuit, short-circuit elementsare disposed in the stator.

Put otherwise, transverse flux electrical machines include a circularstator and a circular rotor, which are separated by an air space calledair gap, that allows a free rotation of the rotor with respect to thestator, and wherein the stator comprises soft iron cores, that directthe magnetic flux in a direction that is mainly perpendicular to thedirection of rotation of the rotor. The stator of transverse fluxelectrical machines also comprises electrical conductors, defining atoroid coil, which is coiled in a direction that is parallel to thedirection of rotation of the machine. In this type of machine, the rotorcomprises a plurality of identical permanent magnet parts, which aredisposed so as to create an alternated magnetic flux in the direction ofthe air gap. This magnetic flux goes through the air gap with a radialorientation and penetrates the soft iron cores of the stator, whichdirects this magnetic flux around the electrical conductors.

In the transverse flux electrical machine of the type comprising arotor, which is made of a plurality of identical permanent magnet parts,and of magnetic flux concentrators, the permanent magnets are orientedin such a manner that their magnetization direction is parallel to thedirection of rotation of the rotor. Magnetic flux concentrators areinserted between the permanent magnets and redirect the magnetic fluxproduced by the permanent magnets, radially towards the air gap.

The transverse flux electrical machine includes a stator, whichcomprises horseshoe shaped soft iron cores, which are oriented in such amanner that the magnetic flux that circulates inside these cores, isdirected in a direction that is mainly perpendicular to the axis ofrotation of the rotor.

The perpendicular orientation of the magnetic flux in the cores of thestator, with respect to the rotation direction, gives to transverse fluxelectrical machines a high ratio of mechanical torque per weight unit ofthe electrical machine. These TFPM alternators are also known togenerate significant cogging torque and ripple torque.

Cogging torque of electrical machines is the torque due to theinteraction between the permanent magnets of the rotor and the statorslots of a Permanent Magnet (PM) machine. It is also known as detent or‘no-current’ torque having a variable reluctance function of theposition. This torque is position dependent and its periodicity perrevolution depends on the number of magnetic poles on the stator.Typically, the fundamental frequency of the torque is twice the standardtorque of the alternator and, in theory, produces a zero energy balance(when losses are neglected). Cogging torque is an undesirable componentfor the operation of such an electrical machine. It is especiallyprominent at lower speeds, with the symptom of jerkiness. Cogging torqueresults in torque as well as speed ripple; however, at high speed theelectrical machine moment of inertia can significantly filter out theeffect of cogging torque.

The ripple torque is a variation of the torque in respect of the nominaltorque and is generally stated in percentage. Typically, the fundamentalfrequency of the ripple torque is about three times the fundamentalfrequency of a single phase of the torque in a triphased electricalmachine. Ripple torque is generally represented by an altered sinusoidalwave. The ripple torque in electrical machines is caused by many factorssuch as cogging torque, the interaction between the MMF and the air gapflux harmonics, or mechanical imbalances, e.g. eccentricity of therotor. Ripple torque is defined as the percentage of the differencebetween the maximum torque Tmax and the minimum torque Tmin compared tothe average torque Tavg:

((Tmax−Tmin)/Tavg)×100   Equation 1

Ripple torque in electrical machines is generally undesirable, since itcauses vibrations and noise, and might reduce the lifetime of themachine. Extensive ripple torque can require measures such changes tothe machine geometry that might reduce the general performance of themachine.

Under load, there is an additional component contributing to the rippletorque in addition to the cogging torque: Ripple torque due to theinteraction between the magneto motive force (MMF) and the air gap fluxharmonics. This component can be influenced by changes to the geometryof the electrical machine.

A machine with a low cogging torque might have a high ripple torquewhereas a machine with a high cogging torque might have a low rippletorque. The interaction between the MMF and air gap flux harmonics cancompensate or increase the cogging torque or ripple torque in differentcases. Cogging torque cannot be acted upon by a change in voltage orcurrent.

It is therefore desirable to produce an electrical machine producing lowvibrations, cogging torque and low ripple torque. It is furthermoredesirable to provide an electrical machine that minimizes recourse toelectrical adjustments to minimize vibrations, cogging torque and rippletorque. It is also desirable to provide an electrical machine that iseconomical to produce. Other deficiencies will become apparent to oneskilled in the art to which the invention pertains in view of thefollowing summary and detailed description with its appended figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a TFEM in accordance with at least oneembodiment of the invention;

FIG. 2 is an isometric view of a TFEM in accordance with at least oneembodiment of the invention;

FIG. 3 is a right side elevational view of a TFEM in accordance with atleast one embodiment of the invention;

FIG. 4 is a left side elevational view of a TFEM in accordance with atleast one embodiment of the invention;

FIG. 5 is a top plan view of a TFEM in accordance with at least oneembodiment of the invention;

FIG. 6 is a bottom plan view of a TFEM in accordance with at least oneembodiment of the invention;

FIG. 7 is a front elevational view of a TFEM in accordance with at leastone embodiment of the invention;

FIG. 8 is a rear elevational view of a TFEM in accordance with at leastone embodiment of the invention;

FIG. 9 is an isometric semi-exploded view of a TFEM illustrating astator portion and a rotor portion in accordance with at least oneembodiment of the invention;

FIG. 10 is an isometric semi-exploded view of a portion of a TFEMillustrating a rotor portion in accordance with at least one embodimentof the invention;

FIG. 11 is an isometric semi-exploded view of a TFEM illustratingmultiple phase modules of a stator portion in accordance with at leastone embodiment of the invention;

FIG. 12 is a magnified section of an isometric semi-exploded view of aTFEM in accordance with at least one embodiment of the invention;

FIG. 13 is a section view of a TFEM illustrating multiple phase modulesin accordance with at least one embodiment of the invention;

FIG. 14 is a section view of a TFEM illustrating cores pairs in a statorportion in accordance with at least one embodiment of the invention;

FIG. 15 an isometric view of a core in accordance with at least oneembodiment of the invention;

FIG. 16 an isometric semi-exploded view of a phase module of a statorportion in accordance with at least one embodiment of the invention;

FIG. 17 an isometric semi-exploded view of an angular portion inaccordance with at least one embodiment of the invention;

FIG. 18 an isometric partial assembly of a phase module in accordancewith at least one embodiment of the invention;

FIG. 19 a front elevational view of an angular portion illustratingrelative angles between a plurality of cores in accordance with at leastone embodiment of the invention;

FIG. 20 a front elevational view of a phase module illustrating relativeangles thereof in accordance with at least one embodiment of theinvention;

FIG. 21 a side elevational view of a rotor portion in accordance with atleast one embodiment of the invention;

FIG. 22 an isometric view of a portion of a coil and cores assembly inaccordance with at least one embodiment of the invention;

FIG. 23 is a front elevational view of a portion of a coil and coresassembly in accordance with at least one embodiment of the invention;

FIG. 24 is a side elevational view of a linear TFEM in accordance withat least one embodiment of the invention; and

FIG. 25 is a isometric view of a linear TFEM in accordance with at leastone embodiment of the invention.

SUMMARY OF THE INVENTION

It is one aspect of the present invention to alleviate one or more ofthe shortcomings of background art by addressing one or more of theexisting needs in the art.

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an extensive overview of the invention. It is notintended to identify key/critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome concepts of the invention in a simplified form as a prelude to themore detailed description that is presented later.

An object of the invention is generally described as an electricalmachine (rotatable or linear) adapted to minimize, reduce or cancels thecogging torque and the ripple torque in a transverse flux electricalmachine.

Generally, an object of the present invention provides a Transverse FluxElectrical Machine (TFEM), which can also be more specificallyappreciated as Transverse Flux Permanent Magnet (TFPM), that hasreduced, or cancelled, cogging torque and ripple torque, collectively orseparately. The reduction, or the cancellation, of the cogging torqueand the ripple torque is made using a structure using various elements,namely: a number of pairs of poles, a magnetic length of the magnets, acoil length, a coil height, a magnet height, a rotor skew, a statorskew, a rotor overlap, a stator overlap and sets of poles.

Generally, an object of the invention provides a phase shift generallyset at 120° electrical to provide standard symmetrical electric currentoverlapping over a complete 360° electrical cycle. The 120° phase shiftallows to, in theory, eliminate harmonics that are not multiples ofthree (3). Therefore an object of the present invention provides anapparatus that substantially reduces harmonics that are multiples ofthree (3) in a three-phase transverse flux electrical machine. A twophases electrical machine would have a 90° phase shift and would use asimilar logic.

One object of the invention provides a cores distribution in a phasethat improves the torque waveform into a smoother, more sinusoidal,waveform.

At least one object of the invention provides at least one phaseincluding a plurality of cores, and associated poles, angularly spacesapart from one another with different angular distances.

At lease one aspect of the invention provides at least one phaseincluding at least three adjacent cores, and associated poles, angularlydistanced apart with a substantially similar angular distance andfurther angularly spaced apart from adjacent cores, and associatedpoles, with a different angular distance.

At least one aspect of the invention provides at least two adjacentcores, and associated poles, angularly radially separated with an angleof 10.8° and angularly radially separated from adjacent cores with atleast one significantly different angle.

At least one object of the invention provides a set of poles, andintervening angular distance therebetween, that is repeated at least twotimes in a phase to locate the poles in the phase.

At least one object of the invention provides a phase including aplurality of similar angular portions, each including a plurality ofcores disposed therein with similar intervening angles thereof. Further,an aspect of the invention provides a phase including a plurality ofassembled angular portions that respectively includes a repeatedsequence of angular distances between the cores.

At least one aspect of the invention provides a phase including aplurality of identical angular portions thereof.

At least one object of the invention provides a TFEM that includes astator skewing in respect with the rotation axis of the TFEM to reduceor cancel, collectively or separately, the cogging torque and the rippletorque of the TFEM.

At least one aspect of the invention provides a TFEM that includes astator skewing of most preferably 6°.

At least one aspect of the invention provides a TFEM that includes astator skewing of preferably between 4° and 8°.

At least one aspect of the invention provides a TFEM that includes astator skewing of between 0° and 11°.

At least one object of the invention provides a TFEM that includes arotor skewing in respect with the rotation axis of the TFEM to reduce orcancel, collectively or separately, the cogging torque and the rippletorque of the TFEM.

At least one aspect of the invention provides a TFEM that includes arotor skewing of most preferably 0°.

At least one aspect of the invention provides a TFEM that includes arotor skewing of preferably between 0° and 8°.

At least one aspect of the invention provides a TFEM that includes arotor skewing of between 0° and 11°.

At least one object of the invention provides a TFEM that includes anumber of pairs of poles that is a multiple of two (2), and desirably amultiple of four (4) to reduce or cancel, collectively or separately,the cogging torque and the ripple torque of the TFEM.

At least one aspect of the invention provides a TFEM that mostpreferably includes 32 pairs of poles per phase.

At least one aspect of the invention provides a TFEM that preferablyincludes between 28 and 36 pairs of poles per phase.

At least one aspect of the invention provides a TFEM that includesbetween 20 to 44 pairs of poles per phase.

At least one object of the invention provides a TFEM that includes amagnetic length that is proportionally used by other elements to reduce,or cancel, collectively or separately, the cogging torque and the rippletorque of the TFEM.

At least one aspect of the invention provides a TFEM that includes amagnetic length of most preferably 100 mm.

At least one aspect of the invention provides a TFEM that includes amagnetic length of most preferably between 60 mm and 150 mm.

At least one aspect of the invention provides a TFEM that includes amagnetic length of between 40 mm and 200 mm.

At least one object of the invention provides a TFEM that includes acoil length sized proportionally to the magnetic length to reduce orcancel, collectively or separately, the cogging torque and the rippletorque of the TFEM.

At least one aspect of the invention provides a TFEM that includes acoil length of most preferably 23% of the magnetic length.

At least one aspect of the invention provides a TFEM that includes acoil length of preferably between 20% and 25% of the magnetic length.

At least one aspect of the invention provides a TFEM that includes acoil length of between 11% and 33% of the magnetic length.

At least one object of the invention provides a TFEM that includes acoil height sized proportionally to the magnetic length to reduce orcancel, collectively or separately, the cogging torque and the rippletorque of the TFEM.

At least one aspect of the invention provides a TFEM that includes acoil height of most preferably 100% of the magnetic length.

At least one aspect of the invention provides a TFEM that includes acoil height of preferably between 70% and 120% of the magnetic length.

At least one aspect of the invention provides a TFEM that includes acoil height of between 40% and 150% of the magnetic length.

At least one object of the invention provides a TFEM that includes amagnet height sized proportionally to the magnetic length to reduce orcancel, collectively or separately, the cogging torque and the rippletorque of the TFEM.

At least one aspect of the invention provides a TFEM that includes amagnet height of most preferably 25% of the magnetic length.

At least one aspect of the invention provides a TFEM that includes amagnet height of preferably between 22% and 29% of the magnetic length.

At least one aspect of the invention provides a TFEM that includes amagnet height of between 17% and 33% of the magnetic length.

At least one object of the invention provides a TFEM that includes arotor overlap to reduce or cancel, collectively or separately, thecogging torque and the ripple torque of the TFEM.

At least one aspect of the invention provides a TFEM that includes arotor overlap of most preferably 0%.

At least one aspect of the invention provides a TFEM that includes arotor overlap of preferably between 0% and 8%.

At least one aspect of the invention provides a TFEM that includes arotor overlap of between −10% and 35%.

At least one object of the invention provides a TFEM that includes astator overlap to reduce or cancel, collectively or separately, thecogging torque and the ripple torque of the transverse flux electricalmachine.

At least one aspect of the invention provides a TFPM that includes astator overlap of most preferably 20%.

At least one aspect of the invention provides a TFEM that includes astator overlap of preferably between 0% and 25%.

At least one aspect of the invention provides a TFEM that includes astator overlap of between −5% and 30%.

At least one object of the invention provides a TFEM that includes adiameter at the air gap that is material to reduce or cancel,collectively or separately, the cogging torque and the ripple torque ofthe TFEM.

At least one aspect of the invention provides a TFEM that includes adiameter at the air gap of most preferably 510 mm.

At least one aspect of the invention provides a TFEM that includes adiameter at the air gap of preferably between 200 mm and 2200 mm.

At least one aspect of the invention provides a TFEM that includes adiameter at the air gap of between 100 mm and 4000 mm.

At least one object of the invention provides a TFEM that includes arotor portion that has a symmetrical layout of magnets and concentratorsaffixed thereon.

At least one object of the invention provides a TFEM that includes astator portion that has a non-symmetrical layout of cores securedtherein.

At least one object of the invention provides a rotatable transverseflux electrical machine (TFEM) comprising a stator portion; and a rotorportion rotatably located in respect with the stator portion, the rotorportion including an alternate sequence of magnets and concentratorsradially disposed about a rotation axis thereof; the stator portionincluding at least one phase, the at least one phase including aplurality of cores cooperating with a coil disposed about the rotationaxis, each core including a skewed pair of poles to progressivelyelectromagnetically engage an electromagnetic field of respectivecooperating concentrators.

At least one object of the invention provides a rotatable transverseflux electrical machine (TFEM) kit comprising a stator portion; and arotor portion adapted to be rotatably located in respect with the statorportion to allow magnets, concentrators and coils cooperation, the rotorportion including an alternate sequence of magnets and concentratorsradially disposed about a rotation axis thereof, the stator portionincluding at least one phase, the at least one phase including aplurality of cores cooperating with a coil disposed about the rotationaxis, each core including a skewed pair of poles to progressivelyelectromagnetically engage an electromagnetic field of respectivecooperating concentrators.

Embodiments of the present invention each have at least one of theabove-mentioned objects and/or aspects, but do not necessarily have allof them. It should be understood that some aspects of the presentinvention that have resulted from attempting to attain theabove-mentioned objects may not satisfy these objects and/or may satisfyother objects not specifically recited herein.

Additional and/or alternative features, aspects, and advantages ofembodiments of the present invention will become apparent from thefollowing description, the accompanying drawings, and the appendedclaims.

DESCRIPTION OF EMBODIMENT(S) OF THE INVENTION

Our work is now described with reference to the Figures. In thefollowing description, for purposes of explanation, numerous specificdetails are set forth in order to provide a thorough understanding ofthe present invention by way of embodiment(s). It may be evident,however, that the present invention may be practiced without thesespecific details. In other instances, when applicable, well-knownstructures and devices are shown in block diagram form in order tofacilitate describing the present invention.

The embodiments illustrated below depict a TFEM 10 with thirty-two (32)poles and a 510 mm diameter at the air gap and a 100 mm length of themagnets. The configuration of the TFEM 10, an external rotor instead ofan internal rotor, the number of phases can change in accordance withthe desired power output, toque and rotational speed without departingfrom the scope of the present invention.

A TFEM 10 is illustrated in FIG. 1 through FIG. 8. The TFEM 10 includesa stator portion 14 and a rotor portion 18. The stator portion 14 isadapted to remain fixed while the rotor portion 18 is located within thestator portion 14 and is adapted to rotate in respect with the statorportion 14 about rotation axis 22. The TFEM of the illustratedembodiments has a modular construction. Two axial side members 26 aresecured together to assemble three electrical phases 30 together, eachbeing provided by a phase module 32. Each phase module 32 is adapted toindividually provide an electrical phase 30 of alternating current. Thepresent embodiment illustrates three phases 30 axially coupled togetherto provide tri-phased current when the TFEM 10 is rotatably actuated.The pair of axial side members 26 interconnects and axially securestogether the three phases 30. Proper tension is applied to each of theplurality of axial securing members 34 to ensure the phase modules 32remain fixedly secured together. In the present embodiment, each axialside member 26 is provided with a series of extending axial securingmember receiving portions 38 adapted to receive the axial securingmembers 34 therein while the axial securing members 34 extends axiallyoutside the phase modules 32. The axial securing members 34 couldalternatively pass through the phase modules 32 in another unillustratedembodiment.

Still referring to FIG. 1 through FIG. 8, the axial side members 26 canbe made of steel or other suitable material providing sufficientmechanical strength for the required purpose. Each axial side members 26is optionally provided with a lifting link 42 sized and designed toreceive therein, for example, a crane hook (not illustrated) to lift andmove the TFEM 10. The axial side members 26 are further equipped with asupport portion 46 adapted to secured thereto a pair of feet 50configured to interconnect both axial side members 26 together and tofurther facilitate securing the TFEM 10 to a base chassis (notillustrated). For instance, the base chassis can be a nacelle when theTFEM 10 is installed in a windmill or alternatively any other chassisprovided by the equipment the TFEM 10 is operatively connected to.

Each axial side member 26 is configured to receive and secure thereto anaxial rotor support member 54. The axial rotor support member 54 isrecessed in a circular cavity 56 (visible in FIG. 9) defined in itsassociated axial side member 26 to concentrically locate the rotorportion 18 in respect with the stator portion 14. The axial rotorsupport member 54 is further removably secured to its associated axialside member 26 with a plurality of fasteners 58. The actualconfiguration of the embodiment illustrated in FIG. 9 allows removal ofthe rotor portion 18 in one axial direction 60 when both axial rotorsupport members 54 are unsecured from their respective axial side member26 because the circular cavities 56 are both located on the same side oftheir respective axial side member 26. This allows for easy maintenanceof the TFEM 10 once installed in its operating configuration with itsexternal mechanism.

As it is also possible to appreciate from the embodiment illustrated inFIGS. 1 through 8, the rotor portion 18 extends through the axial rotorsupport members 54 and rotatably engages both axial rotor support member54. A solid rotor drive member 62 further extends from one axial rotorsupport members 54. The solid drive member 62 could alternatively be ahollowed drive member in another unillustrated embodiment. The drivemember 62 is adapted to transmit rotatable motive power from an externalmechanism (not illustrated) to the TFEM 10 and includes a drive securingmechanism 66 adapted to rotatably couple the drive member 62 of the TFEM10 to a corresponding rotatable drive element from the externalmechanism (not illustrated). The external mechanism (not illustrated)could, for example, be a windmill rotatable hub (not illustrated) towhich the rotor blades (not illustrated) are secured to transmitrotational motive power to the TFEM 10. The external mechanism expressedabove is a non-limitative example and other external mechanisms adaptedto transmit rotational motive power to the TFEM 10 are considered toremain within the scope of the present application.

The TFEM 10 is further equipped with a protective plate 70 adapted tostore and protect electrical connectors and electrical wires thatextends from the TFEM 10 through an electrical outlet 74.

Turning now to FIG. 9 illustrating a semi-exploded TFEM 10 where askilled reader can appreciate the depicted rotor portion 18 is axiallyextracted 60 from the stator portion 14. The rotor portion 18 is axiallyextracted 60 from the stator portion 14 by removing the plurality offasteners 58 and unsecuring the axial rotor support members 54 fromtheir respective associated axial side member 26. It can be appreciatedthat the rotor portion 18 of the exemplary embodiment has three distinctmodular phases 36, each providing an electrical phase 30, adapted toaxially align and operatively cooperate with the three phase modules 32of the exemplified stator portion 14.

FIG. 10 illustrates a further exploded view of the rotor portion 18. Asindicated above, the rotor portion 18 is adapted to rotate in respectwith the stator portion 14. The speed of rotation can differ dependingof the intended purpose. Power remains function of the torque and therotation speed of the rotor portion 18 therefore the TFEM is going toproduce more power if the TFEM rotates rapidly as long as its operatingtemperature remains in the operating range of its different parts toprevent any deterioration (e.g. magnet demagnetization or insulatingvanish deterioration, to name a few. The axial rotor support members 54are adapted to be unsecured from the bearing holder 78 by removing theplurality of fasteners 82. A sequence of assembled seal 86, bearing 90and bearing holder 78 is used on the front side of the rotor portion 18while the same type of assembly is used on the opposite axial side ofthe rotor portion 18 to rotatably secure the rotor 80 to the axial rotorsupport members 54. FIG. 10 also illustrates that each phase module 36of the rotor 80 uses a sequence of alternating permanent magnets 94 andconcentrators 98. Strong permanent magnets 94 can be made of Nb—Fe—B asoffered by Hitachi Metals Ltd and NEOMAX Co. Ltd. Alternatively,suitable magnets can be obtained by Magnequench Inc. and part of thistechnology can be appreciated in patents U.S. Pat. No. 5,411,608, U.S.Pat. No. 5,645,651, U.S. Pat. No. 6,183, 572, U.S. Pat. No. 6,478,890,U.S. Pat. No. 6,979,409 and U.S. Pat. No. 7,144,463.

A semi-exploded stator portion 14 is illustrated in FIG. 11. The axialside members 26 are exploded from the illustrative three (3) phasemodules 32. Each phase module 32 is going to be discussed in moredetails below. However, a positioning mechanism 102 is provided topolarly locate each phase module 32 in respect with its adjacent phasemodule 32 so that proper phase shift is maintained. Generally, the phaseshift is set at 120° electrical to provide standard symmetrical electriccurrent overlapping over a complete 360° electrical cycle. The 120°phase shift allows to, in theory, eliminate harmonics that are notmultiples of three (3). The 120° phase shift illustrated herein is apreferred embodiment and is not intended to limit the angular phaseshift of the present invention.

The illustrative embodiment of FIG. 11 includes three (3) phase modules32. Another possible embodiment includes a multiple of three (3) phasesmodules 32 mechanically secured together, like the three (3) phasemodules of FIG. 11, and electrically connected by phase 30 to increasethe capacity of the TFEM 10 by simply increasing the axial length of theTFEM 10. Thus, a nine (9) phase modules 32 would be coupledthree-by-three for a three-phased 30 TFEM 10. Another embodiment is aone-phase 30 TFEM 10 including only one phase module 32. One otherembodiment could be a two-phased 30 TFEM 10 electrically coupledtogether in a one-phase 30 configuration and with a phase shift of 90°in a two-phase 30 configuration.

As best seen from FIG. 12, each positioning mechanism 102 is embodied asa protruding portion 106 and corresponding cavity 110 sized and designedto mate together to polarly locate two adjacent phase modules 32together. Additionally, each phase module 32 further includes a circularridge 114 on one axial side and corresponding circular groove 118 on theopposite axis side. Engagement of the circular ridge 114 and circulargroove 118 ensures concentric positioning of adjacent phase modules 32along the rotation axis 22 of the TFEM 10. Other shapes, designs and/ormechanical elements suitable to locate the phase modules 32 and theaxial side members 26 together could be used without departing from thescope of the present application. Additionally, the recessed portion 104is further defined in the phase modules 32 and the axial side members 26to facilitate separation of adjacent assembled phase modules 30 andcooperating axial side members 26 by inserting a tool therein and pryingto separate the two adjacent phase modules 32.

A section view of the TFEM 10 is illustrated in FIG. 13. The rotorportion 18 includes a cylindrical frame 122 preferably removably securedto the rotatable drive member 62 with a series of fasteners 128 via twoplates 124 radially extending from the drive member 62. As explainedabove, the cylindrical frame 122 is sized and designed to accommodatethree electrical phases 30, each provided by a phase module 36 includingits alternate series of magnets 94 and concentrators 98 secured thereon.The circular stator portion 14 and the circular rotor portion 18 areseparated by an air space called “air gap” 126 that allows aninterference-free rotation of the rotor portion 18 with respect to thestator portion 14. The smallest is the air gap 126 the most performancethe TFEM is going to have (although cogging torque is going to likely beincreased). Air gap 126 is however limited by mechanical interferencesbetween the stator portion 14 and the rotor portion 18 and is also goingto be influenced by manufacturing and assembly tolerances in addition tothermic expansion of the parts when the TFEM is actuated. The statorportion 14 comprises soft iron cores (cores) 130 that direct themagnetic flux in a direction that is mainly perpendicular to thedirection of rotation of the rotor portion 18. The stator portion 14 ofTFEM 10 also comprises in each phase module 32 electrical conductorsdefining a toroid coil 134 that is coiled in a direction that isparallel to the direction of rotation of the TFEM 10. In thisembodiment, the rotor portion 18 comprises a plurality of identicalpermanent magnets 94, which are disposed so as to create an alternatedmagnetic flux in the direction of the air gap 126. This magnetic fluxgoes through the air gap 126 with a radial orientation and penetratesthe soft iron cores 130 of the stator portion 14, which directs thismagnetic flux around the toroid coil 134.

In the TFEM 10 of the type comprising a rotor portion 18 including aplurality of identical permanent magnets 94 and of magnetic fluxconcentrators 98, the permanent magnets 94 are oriented in such a mannerthat their magnetization direction is parallel to the direction ofrotation of the rotor portion 18, along rotation axis 22. Magnetic fluxconcentrators 98 are disposed between the permanent magnets 94 andredirect the magnetic flux produced by the permanent magnets 94 radiallytowards the air gap 126. In contrast, the stator portion 14 comprises“horseshoe-shaped” soft iron cores 130, which are oriented in such amanner that the magnetic flux that circulates inside these cores 130 isdirected in a direction that is mainly parallel to the direction ofrotation of the rotor portion 18. The perpendicular orientation of themagnetic flux in the cores 130 of the stator portion 14, with respect tothe rotation direction, gives to TFEM a high ratio of mechanical torqueper weight unit of the electrical machine.

The rotor portion 18 has been removed in FIG. 14 illustrating anencumbrance-free section view of the stator portion 14. One canappreciate a plurality of pole faces 138 extending from each core's 130legs 142 (as best seen in FIG. 15). The pole faces 138 are disposed atan angle a from the rotation axis 22 of the TFEM 10. The angle a of thepole faces 138 is called stator skew and is one of a plurality ofelements that can be acted upon to reduce or cancel the ripple torqueand the cogging torque. The elements used to reduce or cancel the rippletorque and the cogging torque are listed below:

TABLE 1 Refer- ence Name Description Unit α Stator The pole faces 138 ofthe cores 130 legs Degree skew are disposed at an angle α from the (°)rotation axis 22 of the TFEM 10. β Rotor skew Axial angle between thelongitudinal Degree axis of the magnets 94 layout on the (°) rotorportion 18 in respect with the rotation axis 22 of the TFEM 10. n Numberof Number of pole faces pairs of the core Integer pairs of 130 in thestator portion 14 extending (#) poles toward the rotation axis 22. Eachcore 130 has two (2) poles extending thereof. The poles number is twicethe number of pairs of poles. 162 Magnetic Axial length of magnets onthe rotor Milli- length portion 18. meter (mm) 166 Coil length Axiallength of the coil 134. Milli- meter (mm) 170 Coil height Radial heightof the coil 134. Milli- meter (mm) 174 Magnet Radial height of themagnet 94. Milli- height meter (mm) 186 Rotor Overlapping ofconcentrators 98 in re- Percent overlap spect with their “normal” sizecorre- (%) sponding to ¼ of a pole pitch. The pole pitch is the angularwidth of two mag- nets 94 in addition to the angular width of twoconcentrators 98. A positive overlap implies fewer magnets 94. 202Stator Overlapping of core 130 in respect with Percent overlap their“normal” size corresponding (%) to ¼ of a pole pitch. The pole pitch isthe angular width of two magnets 94 in addition to the angular width oftwo concentrators 98. A positive overlap implies a ticker core 130. 178Diameter at This is the measured diameter of the Milli- the air gap TFEM10 from one air gap 126 to the meter opposite air gap 126 when themeasure (mm) is made through the rotation axis 22 of the TFEM 10.

Focusing on the stator skew element, in reference with FIG. 14 throughFIG. 18, a plurality of cores 130 are disposed in each phase module 32of the stator portion 14. Each core 130 includes a pair of poles 144(one pair of poles=n=1) extending from respective core's legs 142 (notvisible in FIG. 14). Each pole 130 ends with respective pole faces 138that can be seen inside the stator module 14 illustrated in FIG. 14. Theskewed pole faces 138 of an embodiment are a projection toward therotation axis 22 of the angle of the core's legs 142. Each pair of polefaces 138 can be skewed, or angled, to more or less progressively engagethe electromagnetism of the magnets 94 and the concentrators 98 on therotor portion 18, on the other side of the air gap 126, when the rotorportion 18 is operatively assembled with the stator portion 14. Theangle a of the pole faces 138 of the illustrated embodiment is providedby the angle of the core's legs 142 that is dictated by the design andthe shape of the core-receiving spaces 140 in the phase module 32assembly as illustratively embodied in FIG. 16 and FIG. 17.

In the present embodiment, as shown in FIG. 16, each stator phase module33 is built with a sufficiently mechanically resistant material machinedto form proper shapes therein and includes four angular portions 146(for instance, four angular portions 146 of90°[mechanical]each=360°[mechanical] once assembled together for acomplete stator phase module 32) that are assembled together to locateand secure the cores 130 and the coil 134 within the phase module 32.The embodiment illustrated in FIG. 16 uses four (4) angular portions 146and could alternatively use a different number of angular portions aslong as they complete 360°[mechanical] without departing from the scopeof the present application. In the present embodiment illustrated inFIG. 17, each angular portion 146 in composed of two halves 150 securedtogether with fasteners 154 and further respectively located with pins158. The halves 150 are sized and designed to receive therein apredetermined number of cores 130 with a precise stator skew angle a.One can appreciate that the distances between the sides of the angularportion 146 and their first respective adjacent core 130 is not the sameon each halve 150 because of the core 130 skewing. This could have aninfluence on reference locations of the angles indicated in FIG. 19 andFIG. 20 depending of the reference point used to locate the cores 130.

FIG. 18 depicts some isolated cores 130 and associated coil 134sub-assemblies to more clearly illustrate the angle a of the statorskew. The cores 130 and the coil 134 are in the same position as if theywere within their angular portion 146 (not illustrated), both halves 150(not illustrated) of the angular portion 146 however, has been removedso that a reader can better appreciate the relative position of thecores 130 and the coil 134 in the assembly. From FIG. 18 the skilledreader can appreciate that the cores 130 are collectively disposedprecisely at angle α to provide the desired stator skew and alsorespectively disposed at predetermined angular distances from eachother.

Moving now to FIG. 19 and FIG. 20, a skilled reader can appreciate theangles about which are respectively polarly located the cores 130 in aphase module 32. The angles are applied to four (4) angular portions 146of the embodiment (as indicated above, the illustrated embodiment hasfour (4) angular portions of 90° each). The relative angles are to beconsidered between a same reference point on each core 130. Morespecifically, FIG. 19 depicts an angular portion 146 including eight (8)poles 136 respectively identified C1-C8. In this embodiment, poles C1-C4form a set 148 of poles 136 where the intervening angles(10.781°[mechanical]) between the repeated angular sequences of poles A,B, C, D is constant. The intervening angle (10.781°[mechanical]) couldbe different and remain constant if the number of cores 130 present in aset 148 of poles 136 is different without departing from the scope ofthe present application.

A set 148 of poles 136 is repeated with intervening radial angle 152that has a value adapted to complete an angle of 45°[mechanical] 156 inthe present illustrative embodiment. The actual intervening angle 152 ofthe illustrated embodiment is 12.656°[mechanical] and this angle,required to complete the angle of 45° of the embodiment, could bedifferent should another configuration of set 148 of poles 136 bedesirable. In other words, a new set of poles 148 begins each45°[mechanical] and is repeated a number of times in the presentconfiguration. The number of sets 148 in the illustrative embodiment iseight (8), two per angular portion 146 of 90°. The angle of 45° of theembodiment is 360°[mechanical]/8 and could alternatively be 30°, 60° or90° and fit in the angular portion 146 of 90° in the illustratedembodiment.

Another unillustrated embodiment of sets 148 includes two (2) cores 130with a predetermined intervening angular distance (or angle thereof).The set 148 of two cores 130 is separated from the next set 148 of twocores 130 with a different intervening angular distance. This alternatearrangement of sets 148 repetition is used to build a complete coremodule 32.

One can appreciate from the illustrated embodiment that the cores 130are identical and their respective locations dictates the respectivelocations of their associated poles 136. Other possible embodiment coulduse cores 130 that are not all identical and the location the poles 136should prevail to ensure proper function of the TFEM.

Another element is the rotor skew exemplified by angle β in FIG. 21,depicting a stator 80. There are superposed a first polar layout ofmagnets 94 and intervening concentrators 98 (in solid lines) parallellydisposed in respect with the rotation axis 22 at a 0° angle thereof. Theskewed rotor configuration is represented by a second schematic (andincomplete) polar layout of magnets 94 and intervening concentrators 98(in dotted lines) disposed on the rotor 80 at an angle β in respect withthe rotation axis 22. The three (3) phases 30 preferably use the sameangle for the layout or magnets 94 and concentrators 98 with therotation axis 22. Similarly, the progressive electromagneticinterference with the cores 130 (not shown in FIG. 20) has an effect onthe ripple torque and cogging torque discussed above. The three phases30 of the rotor portion 18 illustrated in FIG. 21 are axially alignedand could alternatively be phase shifted, for example by 120°, from oneanother, to replace or complement a phase shifted stator.

Yet another element to consider is the number of pairs of poles n. Thenumber of pairs of poles n is equal to the number of cores 130 giventhat there are two poles 138 per core 130. The number of magnets 94 isequal to the number of concentrators 98 and their number is twice thenumber of pairs of poles n and consequently also twice the number ofcores 130. The number of pairs of poles n is preferably 32 asexemplified in the present application. Turning now to FIG. 22 whereother elements like the magnetic length 162, the coil length 166, thecoil height 170 and the magnet height 174 are illustrated in a schematicillustration of a partial core 130 assembly, with a coil 134, inconjunction with an alternate suite of magnets 94 and concentrators 98.The magnetic length 162 of the illustrative embodiment use a singlemagnet 94 however, multiple adjacent smaller magnets 94 (notillustrated) could be longitudinally cooperating to replace a singlelonger magnet 94. As one can appreciate from FIG. 22, each core 130extends to two adjacent magnets 94 or two adjacent concentrators 98. Theair gap 126 between the core 130 and the magnets 94 and concentrators 98is also identified.

The overlap rotor is a proportion of a tangential width of theconcentrators 98 in respect with the tangential width of the magnets 94.A pole pitch 182 is establish on the basis that 360° [electrical] on therotor 80 is represented by two (2) concentrators 98 and two (2) magnets94 having a same width. Their collective width is equal to one (1);hence, the width of a magnet 94 and the width of a concentrator 98 is25% of their collective width. A rotor overlap 186 of 0% means that thewidth of the concentrators 190, 98 is equal to the width of the magnets194, 94 as it is illustrated in FIG. 23. A way to separate a complete360° [electrical] cycle on the rotor 80 implies to cut two equally 198two (2) magnets 94 as it is illustrated in FIG. 22. The optimal rotoroverlap 186 indicated in Table 2 below is 0%. 0% rotor overlap 186translates in a width of the concentrators 190, 98 that is equal to thewidth of the magnets 194, 94. In contrast, a 25% rotor overlap 186 meansthat the width of the concentrators 190, 98 is 25% longer than the widthof the magnets 194, 94 for a same pole pitch 182. In other words, theconcentrators 190 are taking 25% more space than the magnets 94 and lessmagnet material is required to build a rotor 80.

The same principle is applied to the stator overlap 202. The overlapstator is a proportion of a tangential width of the core's leg 142 inrespect with the pole pitch 182. The pole pitch 182 is established onthe same basis that 360° [electrical] on the stator is represented bythe same tangential length of two (2) concentrators 98 and two (2)magnets 94. The nominal width 206 of a core's leg 142 is 25% of the polepitch 182. A stator overlap 202 of 0% means that the width 206 of thecore's leg 142 is 25% of the pole pitch 182. The remaining added widths210, 214 and 218 should represent 50% of the pole pitch 182. The optimalstator overlap 202 indicated in Table 2 below is 20%. 20% stator overlap202 translates in a width 206 of the core's leg 142 is 20% more than 25%of the pole pitch 182.

Following in Table 2, is presented a set of preferred ranges about whicheach elements discussed above, material in the reduction or thecancellation of the cogging torque and the ripple torque in a transverseflux electrical machine, are detailed.

TABLE 2 Poor Accept. Average Good Optimal Good Average Accept. Poor n 119 20 27 28  32  36  37  44  45 ∞ 162 0 39 40 59 60 100 150 151 200 201∞ 166 0% 10% 11% 19% 20% 23% 25% 26% 33% 34% ∞ 170 0% 39% 40% 69% 70%100%  120%  121%  150%  151%  ∞ 174 0% 16% 17% 21% 22% 25% 29% 30% 33%34% ∞ β −90° 0° 0° 0° 0° 0° 8° 9° 11° 12° 90° α −90° 0° 0° 4° 4° 6° 8°9° 11° 12° 90° 186 −100%   −11%  −10%   0%  0%  0% 25% 26% 35% 36% 100%202 −100%   −6% −5%  0%  0% 20% 25% 26% 30% 31% 100%

Table 3 below provides quantitative data representing the diameter 178of the TFEM 10 at the air gaps 126. A same number of pairs of poles 138can be used when the diameter 178 changes. It is also possible to addadditional pairs of poles 138 when the diameter 178 is increased and toremove pairs of poles 138 when the diameter is reduced.

TABLE 3 Poor Accept. Average Good Optimal Good Average Accept. Poor 1780 99 100 199 200 510 2200 2201 4000 4001 ∞

FIGS. 24 and 25 illustrate a linear electrical machine that is applyingthe aforementioned features. As a skilled reader can appreciate, theangular dimensions discussed generally in reference with FIG. 19 andFIG. 20 are going to be replaced by equivalent lengths in electricalmachines having a linear configuration. One can see that the alternaterow of magnets 94 and concentrators 98 are in a rectilinear arrangementas opposed to a circular arrangement as explained in reference withFIGS. 1 through 23. A cooperative linear arrangement of cores 130 and alinear coil 134 are also illustrated on the other side of the air gap126. The description made in reference with a rotatable TFEM 10 isapplicable to a linear electrical machine where the stator portion 14becomes a fixed portion and the rotor portion 18 becomes the movableportion. Hence, the angular distance becomes a longitudinal distancealong a longitudinal axis as opposed to the rotational axis 22 used inreference with the rotatable TFEM 10.

The description and the drawings that are presented above are meant tobe illustrative of the present invention. They are not meant to belimiting of the scope of the present invention. Modifications to theembodiments described may be made without departing from the presentinvention, the scope of which is defined by the following claims:

What is claimed is:
 1. A rotatable transverse flux electrical machine(TFEM) comprising: a stator portion; and a rotor portion rotatablylocated in respect with the stator portion, the rotor portion includingan alternate sequence of magnets and concentrators radially disposedabout a rotation axis thereof; the stator portion including at least onephase, the at least one phase including a plurality of cores cooperatingwith a coil disposed about the rotation axis, each core including askewed pair of poles to progressively electromagnetically engage anelectromagnetic field of respective cooperating concentrators.
 2. Therotatable transverse flux electrical machine (TFEM) of claim 1, whereinthe at least one phase is three phases, the three phases being axiallydisposed and phase shifted of 120° of an electrical cycle.
 3. Therotatable transverse flux electrical machine (TFEM) of claim 1, whereina number of pairs of poles is
 32. 4. The rotatable transverse fluxelectrical machine (TFEM) of claim 1, wherein a stator skew is between4° and 8°.
 5. The rotatable transverse flux electrical machine (TFEM) ofclaim 1, wherein a rotor skew is 0° and 8°.
 6. The rotatable transverseflux electrical machine (TFEM) of claim 1, wherein a magnetic length isbetween 60 mm and 150 mm.
 7. The rotatable transverse flux electricalmachine (TFEM) of claim 6, wherein a coil length is between 20% and 25%of the magnetic length.
 8. The rotatable transverse flux electricalmachine (TFEM) of claim 6, wherein a coil height is between 70% and 120%of the magnetic length.
 9. The rotatable transverse flux electricalmachine (TFEM) of claim 6, wherein a magnet height is between 22% and29% of the magnetic length.
 10. The rotatable transverse flux electricalmachine (TFEM) of claim 1, wherein the rotor portion includes a rotoroverlap is between 0% and 25%.
 11. The rotatable transverse fluxelectrical machine (TFEM) of claim 1, wherein the stator portionincludes a stator overlap is between 0% and 25%.
 12. The rotatabletransverse flux electrical machine (TFEM) of claim 1, wherein a diameterof TFEM at an air gap is between 200 mm and 2200 mm.
 13. The rotatabletransverse flux electrical machine (TFEM) of claim 1, wherein the atleast one phase includes at least 2 angular portions.
 14. The rotatabletransverse flux electrical machine (TFEM) of claim 13, wherein oneangular portion includes at least two sets of poles.
 15. The rotatabletransverse flux electrical machine (TFEM) of claim 14, wherein each ofthe at least two sets of poles includes three cores radially located intheir angular portion with a same intervening angle thereof.
 16. Therotatable transverse flux electrical machine (TFEM) of claim 1, whereinthe at least one phase includes at least two sets of poles.
 17. A methodof assembling a rotatable transverse flux electrical machine (TFEM), themethod comprising: providing a stator portion; and assembling a rotorportion rotatably located in respect with the stator portion to allowmagnets, concentrators and coils cooperation, the rotor portionincluding an alternate sequence of magnets and concentrators radiallydisposed about a rotation axis thereof, the stator portion including atleast one phase, the at least one phase including a plurality of corescooperating with a coil disposed about the rotation axis, each coreincluding a skewed pair of poles to progressively electromagneticallyengage an electromagnetic field of respective cooperating concentrators.18. The method of claim 17, wherein the at least one phase is threephases, the three phases being axially disposed and phase shifted of120° of an electrical cycle.
 19. A rotatable transverse flux electricalmachine (TFEM) kit comprising: a stator portion; and a rotor portionadapted to be rotatably located in respect with the stator portion toallow magnets, concentrators and coils cooperation, the rotor portionincluding an alternate sequence of magnets and concentrators radiallydisposed about a rotation axis thereof, the stator portion including atleast one phase, the at least one phase including a plurality of corescooperating with a coil disposed about the rotation axis, each coreincluding a skewed pair of poles to progressively electromagneticallyengage an electromagnetic field of respective cooperating concentrators.20. The transverse flux electrical machine (TFEM) kit of claim 19,wherein a stator skew is between 4° and 8°.